1. Field of The Invention
The present invention relates to an optical packet communication sytem well suited for Local-Area-Network (LAN) and optical switching applications requiring high bit rate transmission. The network is capable of providing multi-gigabit-per-second transmission per user, based on wavelength division multiplexing and frequency routing, and permits users to freely transmit their packets, with collision-free reception. Assuming a single transmitter per user, and either one or two receivers per user, the sytem throughput can approach sixty and ninety percent (per wavelength), respectively.
2. Information Disclosure Statement
Wavelength division multiplexing (WDM) and frequency routing provide the means to build large-capacity packet networks that are optically transparent between input and output ports. In these systems, packets are spatially routed according to their wavelength with minimal transmission loss. Such a network can be realized by using wavelength demultiplexers at the input ports, appropriately connected to similar devices at the output ports, as proposed by Brackett, "Dense Wavelength Division Multiplexing Networks: Principle and Applications". Unfortunately, this arrangement requires N.times.N interconnecting fibers for a system supporting N users. A more practical architecture was recently proposed by Saleh, "Optical WDM Technology for Networking and Switching Applications", based on a compact integrated frequency router invented by Dragone, et al., "Integrated Optics N.times.N Multiplexer on Silicon". In this case, each user is connected to the network by only a pair of fibers in a star configuration, which is well suited for Local-Area-Network (LAN) and optical switching applications. In addition to their routing properties, such sytems can provide contention-free operation, since packets originating from different sources are received on different wavelengths at a given destination, and thus can be demultiplexed and received independently. Unfortunately, N.times.N receivers are mainly required for a system serving N users. An architecture using a single receiver per output port is likely to be more economical. This approach, however, requires the use of fast-tunable optical receivers, and also requires that users be informed of their packet status since packets can be rejected by the receiver. Until now, these two problems have not been satisfactorily resolved. Known reported fast-tunable optical receivers have a too-limited tuning range or are too slow. Several attempts have been made for solving the reception acknowledgement problem, all of which use extensive additional optical hardware which considerably complicates the system architecture. These include Arthurs et al., "Multi-wavelength Optical Crossconnect for Parallel Processing Computers" and "HYPASS: An Optoelectronic Hybrid Packet-Switching System"; and Glance, "Protection-Against-Collision Optical Packet Network". Therefore, none of the inventions of the prior art disclose a network architecture using fast-tunable lasers as transmitters and a novel fast-tunable optical filter for resolving contention between packets. Furthermore, none of the networks disclose an architecture that is simple in that it involves a single optical receiver per output port.